For the last four years, our group has been investigating structure-function relationship of the catalytic domain of avian sarcoma virus (ASV) integrase. We are interested in detailed structural information on the active and inactive enzyme. For that purpose, three data sets for the wild-type ASV IN and its D64N mutant were collected on beamline X9B. The results are: 1) Native enzyme, crystallized from ammonium sulfate; resolution: 1.02 angstrom; Rmerge: 0.056; Completeness: 100.0%; R and Rfree: 0.190 / 0.211 (refined by X-PLOR). 2) Inactive D64N mutant, low pH; Resolution: 1.20 angstrom; Rmerge: 0.060; Completeness: 97.1%; R and Rfree: 0.193 / 0.229 (refined by X-PLOR) 3) Native enzyme, crystallized from PEG; Resolution: 1.06 angstrom; Rmerge: 0.034; Completeness: 90.1%; R and Rfree: 0.200 / 0.233 (refined by X-PLOR).